Method and apparatus for liquid treatment of and liquid extraction on a paper pulp

Abstract

It is desirable to be able to treat medium consistency (e.g. about 8-12% by weight) paper pulp suspensions with treatment liquid (e.g. a wash liquid), and to thicken the pulp to about 30-50% consistency at the same time. A moving (e.g. rotating) channel is defined by a root wall and upstanding side walls--some or all of which are perforated--and treatment liquid is introduced by an arcuately elongated distributor with perforated side walls into the center of the pulp within the channel, filtrate flowing out through the perforated walls. A pivoted wall portion of the stationary housing of the treatment device restricts outflow of the thickened pulp cake from the device, the cake flowing between a doctor blade and the pivoted wall portion.

What is claimed is: 
     
       1. A device for liquid treatment of a suspension of cellulosic fibrous material, comprising: (a) a housing having an outer, essentially solid, wall; including an adjustable portion; p1 (b) means defining a channel having a solid root wall and a pair of side walls with an open face opposite said root wall, the channel being elongated in a dimension and positioned so that the open face thereof is adjacent said housing outer wall, and at least one of said side walls is perforated;   (c) means for moving said root wall, and at least one of said side walls, with respect to said outer wall in the dimension of elongation of said channel;   (d) means for feeding material to be treated into said channel at one portion of said housing;   (e) an outlet for passage of treated material out of said channel and said housing adjacent said adjustable portion of said housing outer wall;   (f) means for introducing treatment fluid into said channel, between said means (d) and (e), through said housing outer wall, so that the treatment fluid passes generally parallel to said root wall, through the material to treat it, and out perforations in at least one of said channel walls; and   (g) means for providing discharge from the housing of liquid that has passed through perforations in at least one of said channel walls.   
     
     
       2. A device as recited in claim 1 wherein said means (f) comprises a hollow distributor extending from the outer wall into the approximate center of said channel between said side walls, said distributor comprising a pair of perforated side walls, and having a significant length in the channel direction of elongation. 
     
     
       3. A device as recited in claim 2 wherein said means (f) side walls are parallel to said channel side walls, and wherein said channel side walls are perforated. 
     
     
       4. A device as recited in claim 3 wherein said channel side walls are perforated plates with linear screens disposed on the interiors thereof. 
     
     
       5. A device as recited in claim 4 wherein said distributor side walls comprise screens, and wherein said distributor has an end wall closely spaced from said root wall, said end wall also comprising a screen. 
     
     
       6. A device as recited in claim 5 further comprising a plurality of nozzles for feeding treatment fluid to said hollow distributor, said nozzles provided along said housing outer wall spaced from each other in the direction of movement of said channel. 
     
     
       7. A device as recited in claim 1 wherein said housing outer wall is arcuate, and wherein said root wall is an arcuate wall of a rotor, said side walls extending radially outwardly therefrom; and wherein said means (c) comprises means for rotating said root wall and rotor about a generally horizontal axis, and wherein said means (f) introduces fluid so that it flows parallel with respect to said axis through the material. 
     
     
       8. A device as recited in claim 7 wherein said rotor has mounted thereto a plurality of said root walls spaced from each other along the axis of rotation of said rotor, each of said root walls has a pair of associated said side walls, cooperating with said housing outer wall, and including said cooperating means (d), (f), (g) and outlet elements. 
     
     
       9. A device as recited in claim 8 wherein said rotor comprises an inner metal tube, a plurality of ribs extending radially outwardly from said inner tube, said arcuate root walls attached to said ribs and radially spaced from said inner tube; and further comprising a shaft keyed to said inner tube. 
     
     
       10. A device as recited in claim 1 wherein said channel side walls are perforated plates with liner screens disposed on the interiors thereof, and said root wall is solid. 
     
     
       11. A device as recited in claim 2 wherein said distributor has an arcuate length of about 80°-180°. 
     
     
       12. A device as recited in claim 11 further comprising a plurality of nozzles for feeding treatment fluid to said hollow distributor, said nozzles provided along said housing outer wall spaced from each other in the direction of movement of said channel. 
     
     
       13. A device as recited in claim 2 wherein said distributor side walls comprise screens, and wherein said distributor has an end wall closely spaced from said root wall, said end wall also comprising a screen. 
     
     
       14. A device as recited in claim 2 further comprising a plurality of nozzles for feeding treatment fluid to said hollow distributor, said nozzles provided along said housing outer wall spaced from each other in the direction of movement of said channel. 
     
     
       15. A device as recited in claim 2 wherein said housing outer wall is arcuate, and wherein said root wall is an arcuate wall of a rotor, said side walls extending radially outwardly therefrom; and wherein said means (c) comprises means for rotating said root wall and rotor about a generally horizontal axis, and wherein said distributor introduces fluid so that it flows parallel with respect to said axis through the material. 
     
     
       16. A device as recited in claim 1 wherein said means (e) includes said adjustable portion of said housing outer wall, and a doctor blade disposed on the opposite side of said channel from the adjustable portion. 
     
     
       17. A method for treating a suspension of cellulosic fibrous material, using an arcuate root wall rotatable about an axis and defining an open channel with a pair of side walls extending radially outwardly with respect to the root wall, at least one of the side walls rotatable with the root wall, and at least one of the channel-defining walls being perforated, said method comprising continuously and progressively: (a) rotating the root wall about an axis;   (b) introducing a suspension of cellulosic fibrous material at a consistency of about 2-16% by weight into the channel;   (c) introducing treatment fluid into the suspension in a center portion of the channel so that the treatment fluid permeates the suspension, flowing parallel with respect to said axis therethrough;   (d) effecting removal of liquid from the channel through perforated walls defining the channel to facilitate treatment and thickening of the suspension; and   (e) discharging suspension having a consistency greater than that of the introduced suspension.   
     
     
       18. A method as recited in claim 17 wherein step (a) is practiced by introducing a suspension having a consistency of about 8-12% into the channel. 
     
     
       19. A method as recited in claim 18 wherein steps (d) and (e) comprise pressing the suspension and discharging a suspension having a consistency of about 30-50%. 
     
     
       20. A method as recited in claim 17 wherein step (c) comprises introducing treatment liquid in a distributor extending into the channel from the open part thereof opposite the root wall so that the treatment liquid flows substantially uniformly into the suspension at all portions along an arcuate extent thereof of about 80°-180°.